1. Field of the Invention
The present invention relates to supplying power to integrated circuits and, more specifically, to the integration of a voltage regulator into the circuit to be supplied voltage. The present invention more specifically relates to linear D.C./D.C. regulators. Such regulators essentially include a control stage and a power stage. The power stage is, most often, formed of a MOS transistor having one power terminal (drain or source) connected to a D.C. supply voltage and the other power terminal (source or drain) providing the regulated voltage. The control gate or terminal of the power transistor is connected to the output of the regulator control stage. This control stage essentially includes a comparator that compares a voltage representative of the regulated output voltage with a reference voltage. This reference voltage is most often provided by a commonly-called bandgap circuit. The operating principle of a series D.C./D.C. regulator is well known in the art. In the present description a power transistor does not refer to a high voltage transistor but to the fact that the power stage must conduct a relatively high supply current (generally ranging between a few tens of milliamperes and approximately one ampere).
2. Discussion of the Related Art
The use of a D.C./D.C. regulator in an integrated circuit is linked to the presence of a supply voltage available on the board where the integrated circuit is implanted, which is greater than the supply voltage of the components internal to the circuit.
An example of application of the present invention is the replacing of an integrated circuit on a printed circuit board with the least possible modifications. For example, technological progress has led to an increasingly advanced miniaturization of integrated circuits, which goes along with a decrease in their supply voltage. To keep on using a given electronic board, designed with a technology designed to use a first supply voltage (for example, 5 V) with an integrated circuit in a more recent technology that uses a lower voltage (for example, 3.3 volts), it is necessary to lower the circuit supply voltage. For this purpose, a first solution is to modify the printed circuit board. However, such a modification is not desirable.
A second solution to which the present invention applies includes integrating a voltage regulator into the integrated circuit. This regulator then has the function of converting the supply voltage present on the board into a supply voltage acceptable for the integrated circuit according to the technology used.
FIG. 1 very schematically shows the structure of a conventional integrated circuit 1 provided with a voltage regulator 2 (REG). Such a circuit 1 is generally essentially formed of a core 3 (C) integrating the different functions associated with the actual application of integrated circuit 1, of input/output circuits (block 4), and of regulator 2. The function of input/output block 4 is to be used as an interface between the integrated circuit core and the outside. It may be, for example, an adaptation of voltage levels between the inside and the outside, electrostatic protection devices and, more generally, electronic circuits (most often, amplifiers) enabling exchange between the inside and the outside of the circuit. Input/output block(s) 4 most often receive the supply voltage HVDD of circuit 1 drawn from the printed circuit board (not shown) through a terminal 8 and a voltage VDD (most often smaller, due to the technology used) corresponding to the operating voltage of core 3 of the integrated circuit. Ground GND of the integrated circuit core and of the input/output block is common. Voltage VDD is provided by regulator 2, which receives voltage HVDD. Core 3 of the integrated circuit communicates with input/output blocks 4 via electronic connections 5. Input/output blocks 4 communicate with the outside of the circuit via connections 6 to terminals 7 of the integrated circuit. In practice, input/output blocks 4 of the integrated circuit are formed in what is called a crown of the circuit. This crown surrounds core 3 of the circuit containing the actual application.
A conventional example of an integrated circuit, of the type described hereabove, is described in an article entitled xe2x80x9cEmbedded 5 V-to-3.3 V Voltage Regulator for Supplying Digital IC""s in 3.3 V CMOS Technologyxe2x80x9d by Gerrit W.den Besten and Bram Nauta, published in the IEEE Journal of Solid-State Circuits, volume 33, nxc2x07, July 1998 which is incorporated herein by reference.
However, the advantages of having an integrated circuit included on a printed circuit board that provides a greater power supply do not outweigh the disadvantages of known integrated-regulator solutions.
A first disadvantage is that there is a series voltage drop due to the lines conveying voltage VDD. Indeed, regulator 2 must provide the power supply for the entire integrated circuit core. In integrated circuits requiring no regulator, that is, able to receive a supply voltage directly from the outside of the circuit, the terminals of application of the supply voltage are generally multiplied to avoid this phenomenon. The voltage drop linked to the line conveying the supply voltage requires adapting the power stage of the regulator to each application, and thus the transistor forming it.
A second disadvantage is that the routing of the wide supply lines in an integrated circuit, based on a single point, is poorly adapted to forming complex integrated circuits using automatic placing and routing tools.
A third disadvantage is that the use of a single pad of terminal 8 for connection to external supply voltage HVDD causes irregular power dissipation in the integrated circuit. Indeed, the higher the power to be provided by the regulator, the more the regulator dissipates. This power dissipation is essentially due to the ballast transistor of its power stage and is thus localized. This results in an undesirable temperature gradient in the integrated circuit. It could be devised to multiply the number of regulators in the integrated circuit to decrease the individual power dissipated by each one of them. Such a solution would bring about several other disadvantages, among which:
a bulk increase of the regulator, and thus of the integrated circuit; and
a problem of distribution of the supply voltages in the integrated circuit. Indeed, a metal level of a multiple-layer integrated circuit is generally used to form a supply distribution grid (routing grid). By multiplying the number of regulators, it is then necessary to divide this grid up. There again, a solution that must be adapted to each case, and thus to each application, is obtained.
Another disadvantage of the existence of a single supply pad outside the package is that this creates significant parasitic inductances on the regulator supply line. Indeed, the higher the number of supply terminals, the more the parasitic inductances due to the connection between the chip and the outside of the package are divided (by being associated in parallel).
It would be desirable to have a linear D.C./D.C. regulator that is versatile by being able to easily adapt to different integrated circuit chips. In particular, the current design of integrated circuit chips uses a library of circuits or individual components that are assembled to implement the desired function. In this regard, the fact of having to adapt the regulator, and especially the sizing of its power stage, to each application negates the beneficial effects of a circuit integrating a voltage regulator.
An object of the present invention is to overcome the disadvantages of known circuits integrating a voltage regulator.
The present invention more specifically aims at providing a novel integrated circuit with an internal voltage regulator that allows use of several terminals for connection to an external supply voltage.
An object of the present invention also is that the internal regulator can provide several connections on the metal level of internal distribution of the integrated circuit supply voltage (routing grid).
The present invention also aims at improving the temperature uniformity in an integrated circuit with an internal regulator.
The present invention also aims at providing a solution that is versatile, that is, that can be transposed to different integrated circuits by simple association of identical elementary cells based on a library of a small number of cells.
The present invention further aims at providing a low-bulk solution.
To achieve these and other objects, the present invention provides an integrated circuit with a D.C./D.C. internal voltage regulator, including at least two power stages of the regulator, having respective terminals for connection to a supply voltage connected to distinct pads of the integrated circuit, and a single control stage.
According to an embodiment of the present invention, the power stages are arranged in an input/output crown of an integrated circuit chip, external to a core of this chip in which is formed, among others and at least partly, the control stage.
According to an embodiment of the present invention, the control stage includes means for generating a reference voltage and a means for comparing a voltage representative of the regulated voltage with this reference voltage, integrated in the core of the chip, and a stage for measuring the regulated voltage, integrated in the chip crown.
According to an embodiment of the present invention, the circuit includes a single power stage, dedicated to the control stage and providing thereto its specific supply voltage.
According to an embodiment of the present invention, each power stage includes a MOS transistor, a first power terminal of which is connected to a pad of the integrated circuit, a second power terminal of which is connected to a terminal of supply of the chip core, the gate of the power transistor being connected to an output of the control stage.
According to an embodiment of the present invention, a filtering means is associated with each power stage.
The present invention also provides a method for integrating a linear regulator into an integrated circuit chip, including integrating a control part into the chip core and at least two power stages into the input/output crown of this chip.
According to an embodiment of the present invention, the number of power stages depends on the power consumption of the chip core.
The foregoing objects, features and advantages of the present invention will be discussed in detail in the following non-limiting description of specific embodiments in connection with the accompanying drawings.